This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Bacteriophages are important conduits for horizontal gene exchange among bacteria and are directly responsible for the virulence of many bacterial pathogens. Phage-encoded virulence factors include the shiga toxins in pathogenic strains of Escherichia coli and the cholera toxin in Vibrio cholerae. Bacteriophages can drive the emergence of new pathogenic bacterial strains through the horizontal transfer of virulence factors and thus an understanding of phage genome evolution has important public health implications. This research project will examine the population genetics and genome evolution of bacteriophages. We will test the hypothesis that much of the genetic diversity within bacteriophage populations and communities can be attributed to recent horizontal genetic exchange events among phages and between phages and bacteria. A natural community of aquatic bacteriophages will be used to address questions about phage genome evolution and the frequency of horizontal gene transfer within populations and communities of aquatic bacteriophages. The specific aims of this research are to: (1) Assess the frequency of horizontal gene transfer events and its influences on bacteriophage genome organization and evolution, (2) Examine the population genetics/genomics of specific bacteriophages to determine the extent to which bacteriophages in the same population carry different alleles of laterally transferred host-derived genes, (3) Analyze the composition and distribution of non-viral, non-host genetic material carried in bacteriophage genomes, and (4) Train undergraduate students in the key molecular genetic techniques used in biomedical research. Students will gain experience in scientific communication, laboratory techniques, use of instrumentation, and bioinformatics as they complete individual projects.